首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   22873篇
  免费   2459篇
  国内免费   1588篇
耳鼻咽喉   156篇
儿科学   359篇
妇产科学   251篇
基础医学   2901篇
口腔科学   347篇
临床医学   3145篇
内科学   3531篇
皮肤病学   213篇
神经病学   1528篇
特种医学   983篇
外国民族医学   20篇
外科学   2060篇
综合类   3560篇
现状与发展   5篇
一般理论   5篇
预防医学   1367篇
眼科学   806篇
药学   2503篇
  33篇
中国医学   1401篇
肿瘤学   1746篇
  2024年   76篇
  2023年   351篇
  2022年   909篇
  2021年   1308篇
  2020年   975篇
  2019年   856篇
  2018年   899篇
  2017年   732篇
  2016年   729篇
  2015年   1003篇
  2014年   1381篇
  2013年   1124篇
  2012年   1663篇
  2011年   1737篇
  2010年   1066篇
  2009年   910篇
  2008年   1122篇
  2007年   1128篇
  2006年   1173篇
  2005年   1069篇
  2004年   677篇
  2003年   719篇
  2002年   599篇
  2001年   463篇
  2000年   582篇
  1999年   563篇
  1998年   375篇
  1997年   374篇
  1996年   272篇
  1995年   253篇
  1994年   213篇
  1993年   130篇
  1992年   206篇
  1991年   147篇
  1990年   130篇
  1989年   106篇
  1988年   110篇
  1987年   101篇
  1986年   97篇
  1985年   79篇
  1984年   36篇
  1983年   30篇
  1982年   25篇
  1979年   35篇
  1974年   35篇
  1973年   27篇
  1969年   31篇
  1968年   23篇
  1967年   29篇
  1966年   30篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
婚姻质量与人格特质的相关分析   总被引:8,自引:0,他引:8  
目的 探究夫妻人格特质与婚姻质量的相关以及夫妻间人格特质的相关性 ,为婚姻咨询提供帮助。方法 用 OL-SON婚姻质量问卷 ( ENRICH)和艾森克人格问卷 ( EPQ) ,对 1 0 0对夫妻进行测试和调查。结果 精神质特质、神经质特质与婚姻质量总分存在极显著负相关 ( P<0 .0 0 1 ) ,掩饰维度与婚姻质量总分存在极显著正相关 ( P<0 .0 0 1 ) ,精神质和神经质均与婚姻质量的 8个因子存在极显著负相关 ( P<0 .0 0 1 ) ,丈夫的神经质与妻子精神质特质间存在显著性正相关 ( P<0 .0 1 ) ,与妻子的掩饰维度存在显著性负相关 ( P<0 .0 5 )。结论 婚姻质量与人格关系极为密切。  相似文献   
142.
神经调节因子及其信号转导机制   总被引:4,自引:1,他引:4  
神经调节因子(NRG)是一个由4种基因编码的多肽家族,包含4种同源异构体NRG-1,2,3和4,其功能性受体是由ErbB酪氨酸激酶受体组成,属于跨膜酪氨酸激酶的表皮生长因子受体家族成员,包括ErbB2/HER2/neu,ErbB3/HERS和ErbB4/HER4.NRG通过诱导ErbB受体构象变化,使ErbB蛋白形成二聚体,继而激活酪氨酸激酶,引起C-末端的自身酪氨酸磷酸化和反式酪氨酸磷酸化,而发挥其生物学作用.  相似文献   
143.
Zou C  Weng W  Deng X  Cheng K  Liu X  Du P  Shen G  Han G 《Biomaterials》2005,26(26):5276-5284
Porous beta-tricalcium phosphate (TCP)/collagen composites with different beta-TCP/collagen weight ratio were prepared. The influences of the preparation conditions on the microstructure of porous composite and the joint status of beta-TCP particles with collagen fibrils were characterized by X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. The results showed: (1) an acid treatment could effectively disassemble collagen fibrils; (2) in the resulting porous composites, beta-TCP particles homogenously existed on the skeleton of the collagen fibril network and bonded tightly to both the fibrils and themselves. The tight bonding formation could be due to the reaction between Ca ions in the particles and carboxyl groups in collagen polypeptide chains and due to the reprecipitation of partially dissolved beta-TCP during synthesis. The tight bonding between beta-TCP particles and collagen fibrils in the composites demonstrated an integrated structure, which was reproducible when beta-TCP/collagen ratio ranged from 2 to 4. Such integrated structure would make significant contributions in reliably tailoring properties of the porous composites by varying beta-TCP content. In addition, the porous composites had large porosity (approximately 95%) and appropriate pore size (approximately 100 microm), showed no negative impact in cytotoxicity assay and complete bone tissue regeneration after 12 weeks in animal test.  相似文献   
144.
Advanced glycation end products (AGEs), the final products of nonenzymatic glycation and oxidation of proteins, are found in the plasma and accumulate in the tissues during aging and at an accelerated rate in diabetes. A novel integral membrane protein, termed receptor for AGE (RAGE), forms a central part of the cell surface binding site for AGEs. Using monospecific, polyclonal antibody raised to human recombinant and bovine RAGE, immunostaining of bovine tissues showed RAGE in the vasculature, endothelium, and smooth muscle cells and in mononuclear cells in the tissues. Consistent with these data, RAGE antigen and mRNA were identified in cultured bovine endothelium, vascular smooth muscle, and monocyte-derived macrophages. RAGE antigen was also visualized in bovine cardiac myocytes as well as in cultures of neonatal rat cardiac myocytes and in neural tissue where motor neurons, peripheral nerves, and a population of cortical neurons were positive. In situ hybridization confirmed the presence of RAGE mRNA in the tissues, and studies with rat PC12 pheochromocytes indicated that they provide a neuronal-related cell culture model for examining RAGE expression. Pathological studies of human atherosclerotic plaques showed infiltration of RAGE-expressing cells in the expanded intima. These results indicate that RAGE is present in multiple tissues and suggest the potential relevance of AGE-RAGE interactions for modulating properties of the vasculature as well as neural and cardiac function, prominent areas of involvement in diabetes and in the normal aging process.  相似文献   
145.
The Drosophila melanogaster proteins Flamingo and Prickle act in the planar cell polarity (PCP) pathway, which is required for acquisition of epithelial polarity in the wing, eye, and epidermis. In mammals, PCP signaling has been shown to regulate cell movements and polarity in a variety of tissues. Here, we show that the murine Flamingo orthologues Celsr1-3 and the Prickle orthologues Prickle1, Prickle2, and Testin have dynamic patterns of expression during pregastrulation and gastrulation stages. Celsr1 is expressed in the anterior visceral endoderm and nascent mesoderm, Celsr2 and Celsr3 mark the prospective neuroectoderm, Prickle1 is expressed in the primitive streak and mesoderm, Prickle2 in the node, and Testin in the anterior visceral endoderm, the extraembryonic ectoderm, primitive streak, and mesoderm. Analysis of a gene-trap mutation in Testin indicates that this gene is not required for embryogenesis; therefore, other Prickle homologues may compensate for its function during development.  相似文献   
146.
147.
将人白细胞介素2(hIL-2)cDNA克隆到逆转录病毒载体MNSM的PL位点 ,分别构建了转录受SV40早期启动子和人甲胎蛋白增强子调控的重组逆转录病毒载体MNSI和MNSIA。用脂质体转染法将MNSI和MNSIA分别转导PA317包装细胞,测质粒转染率为(5~20)×10~(-3)克隆/μgDNA·10~6细胞,病毒感染率为(5.4~450)×10~4CFU/ml。重组病毒在4μg/ml polybrene存在条件下感染人肝癌细胞、肾癌细胞和黑色素瘤细胞,Neo~R克隆经Southernblot分析证明hIL-2cDNA转入人肿瘤细胞并整合, R NA斑点杂交及IL-2活性表达分析证明,人甲胎蛋白增强子可促进异源启动子启动hIL-2cD-NA在合成甲胎蛋白的人肝癌细胞中高效特异转录和表达。该研究对肝癌特异性免疫增强基因治疗有重要意义。  相似文献   
148.
Low grade mucosa-associated lymphoid tissue (MALT) lymphomas commonly arise from a background of chronic inflammatory lesions and can transform into high grade tumors at a late stage. Because chronic inflammation is closely associated with genetic instability, which is one of the mechanisms leading to activation of oncogenes and inactivation of tumor suppressor genes, it is possible that genetic instability plays an important role in MALT lymphomagenesis. In this study, we have examined the frequency of replication error (RER+) phenotype, a newly defined manifestation of genetic instability, and its relationship to p53 mutations in 40 MALT lymphomas (16 high grade and 24 low grade). RER+ phenotype was detected in 21/40 (52.5%) MALT lymphomas (12/24, 50% in low grade; 9/16, 56.2% in high grade). Five of seven reactive lymphoid infiltrates adjacent to tumors also showed one microsatellite alteration, four of which were identified in the corresponding lymphoma lesions in the same patient. In five RER+ high grade lymphomas with low grade lesions, homogeneous and heterogeneous microsatellite alterations were observed between the two components. The same 40 cases were investigated for p53 gene mutations at exons 5 to 8 by PCR-SSCP and direct sequencing. p53 point mutations were found in 11 (27.5%) of the 40 cases. These mutations were statistically related to RER+ phenotype (P < 0.05). Our results demonstrate that the RER+ phenotype is a common genetic feature of MALT lymphomas. Genetic instability occurs throughout the spectrum of the lymphoma development and may be related to the accumulation of genetic aberrations such as p53 mutations. The observation of identical microsatellite alterations between the adjacent lymphoid infiltrates and their corresponding lymphomas provides genetic evidence for evolutionary link of the two lesions. The homogeneous and heterogeneous microsatellite alterations observed between low and high grade components indicate their clonal lineage and genetic diversity.  相似文献   
149.
The immunoreactivity of a range of vascular and non-vascular smooth muscle tumours, rhabdomyosarcomas, and non-myoid lesions has been examined with the use of a monoclonal antibody to smooth muscle-specific actin and the muscle intermediate filament, desmin. In all cases of smooth muscle-derived tumours, the alpha-actin antibody yielded superior results. Staining of the myofibroblasts of fibromatoses was also seen. In contrast to desmin, immunoreactivity was not exhibited by rhabdomyosarcomas. We propose that this monoclonal antibody to alpha-smooth muscle actin is a useful addition to the panel of reagents used for the characterization of soft tissue proliferations and tumours. The technical aspects of the application of this monoclonal antibody to immunohistochemistry are discussed.  相似文献   
150.
本实验用家兔全血加精制大肠杆菌内毒素,体外培养提取粗制家兔内生致热原。给大鼠静脉注射复制发热模型,观察了不同温度保存和不同时间保存的EP对其致热活性的影响。结果表明:4℃保存3天,-40℃保存3天,7天,30天和180天的EP与4℃保存1天的EP比较,其发热第一时相发热峰值和1小时体温反应指数均无显著性差异(P<0.05)。发热第二时相△T和第二时相1小时TRI,在4℃保存3天和-40℃保存3天,  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号